Method of coating metal



Patentecl` Apr. 28, 1936 I UNITED STATES PATENT OFFICE METHOD OF COATING NIETAL Elgin Carleton Domm, Niles, Mich., assignor to National-Standard Company, Niles, Mich., a corporation of Michigan 6 Claims.

This invention relates to improvements in method of coating metal.

In the Crapo Patent No. 1,984,335, issued Dec- 11, 1934, is described a method of coating a ferrous article by hot-galvanizing' it with Zinc, and over that depositing by some other method an additional coating of zinc or a coating of cadmium.

It has now been discovered thata corrosionresisting .coating may be produced which has considerable advantage under certain circumstances, particularly with respect to the type of corrosion of which the salt spray is typical, by applyin a hot-dipped coating of cadmium, and then electroplating a coating of zinc thereon.

The invention is particularly applicable to coating strands of wire to be used in reinforcing the bead of the tire. The wire when so used commonly acts as a tension-member, and is imbedded in a rubber or rubber compound. When so used, the wire is exposed to Corrosive and rusting agents, particularly to moisture which may seep into the tire.

The drawing shows in diagrammatic form an embodimentof my invention.. p

In accordance with the invention, a metal, for example wire suitable for use in tire heads, is first hot-dipped to provide a coating of cadmium. This may be done, for example, by dipping the wire in hot molten cadmium. A coating of zine is then put over the first coat by electrolysis or by electroplating, preferably by lectroplating.

Not only does a double coating applied by the above-mentioned method give very good corrosion resistance, but it has been discovered that the electro-coat tends to fill in the depressions in the lower cadmium coat and thus produce a uniform and sr'nooth coating. This is wholly unexpected.

If desired, copper'or other suitable'material may be applied over the corrosive-resistant coating in order to increase the adhesiveness of the wire to rubber. It is frequently desirable to apply such a coating when wire is used as a reinr forcement for a tire bead.

The new process heren described is especially useful in procuring a coating of a desired and uniform thickness. In practice, I give the wire a hot coat first, and preferably I wipe this thin.

In the next step, when the coating isput on by electroplating, the operation can be continued to give exactly a desired thickness. At the same time the coating acquires a smooth, uniform character which is free from holes, defects, and the like.

The foregoing description has been given for clearness 'of understanding only, and no unnecessary limitations are to be understood therefrom, but the appended claims should be construed as broadly as permissible in View of the prior art.

This application is a division of my co-pending application Serial No. 653549, filed January 25, 1933.

What I regard as new and desire to secure by Letters Patent is:

1. The process of coating a ferrous article which consists in applying to it by the hot-dip process a coating of cadmium, and electrodepositing thereon an outer coating substantially wholly of znc.

2. The method of coating a metal to increase its corrosion resistance comprising first applying to it molten cadmium, and then applying a second coating of zinc by electroplating over the first coating.

3. The method'of producing a ferrous tirebead reinforcement wire of uniform corrosionresistance which comprises first coating a ferrous wire with cadmium by the hot-dip process, and then electro-plating zinc upon the hot-dipped wire to produce a uniform 'coating of desired thickness.

4. A coated ferrous article, comprising a ferrous base having a hot-dipped coating of cadmium thereon, and over that an electrodeposited coating substantially wholly of Zinc..

5. A coated ferrous wire, comprising a ferrous' base wire having a hot-dipped coating of cadmium thereon, and over that an electrodeposited coating substantially wholly of Zinc.

.6. A coated tire bead wire comprising a ferrous base wire having a hot-dipped coating of cadmium thereon, an electrodeposited coating substantially wholly of Zinc thereon, and having a coating of rubber Vulcanized thereto.

ELGIN CARLETON DOMM. 

